Embodiments of the inventive concepts disclosed herein are generally directed to communication systems and methods for unmanned aerial vehicles.
Unmanned aerial vehicles (UAVs) have rapidly matured in recent years from the relatively simple remote controlled airplanes of the past to sophisticated autonomous aircraft that are capable of performing important civilian and military operations and missions. Applications may include but are not limited to aerial surveying, area surveillance, crop monitoring, search and rescue operations, border monitoring, and the like. UAV platforms may range from relatively small hobby class vehicles such as so-called quad-copters equipped with digital cameras that are capable of 10 to 30 minutes of flight time when powered by a battery, to relatively large aircraft such as the Northrop Grumman RQ-4 Global Hawk, which is powered by a jet engine and has endurance of up to 32 hours or more. Interest has recently been growing in the area of groups or swarms of UAVs operating in close proximity to one another to conduct various operations and missions. A group of UAVs flying in a close proximity formation may be capable of performing certain operations that would be difficult or impossible for a single aircraft or UAV to achieve. Examples include terrain mapping, wide angle area surveillance, or flying through hazardous conditions where some number of the UAVs may be lost or damaged by adverse weather conditions, encounters with terrain or vegetation, or opposing forces. In such instances, it may be desirable to configure a plurality (or a swarm) of small UAVs operating together to make loss or attrition of one or more of the UAVs in the swarm less likely to jeopardize the outcome of the objective, and to reduce the total cost to execute the objective.
Some civilian and military operations or missions may need to be conducted at beyond line-of-sight (BLOS) distances far away from any remote control or communication station. BLOS communication may be accomplished by using either satellite communications or the high frequency (HF) band in the frequency range of 3 MHz to 30 MHz. For large UAVs such as the RQ-4 Global Hawk, the aircraft is large enough to accommodate a satellite communication antenna on board, which makes it possible to communicate over BLOS distances from the controlling communication station. With small UAVs such as the type that might be deployed as a group or swarm, satellite communication antennas are too large to be practical at present. Radio waves in the HF band may be reflected back to earth by the ionosphere layer in the atmosphere, which makes BLOS communication across intercontinental distances possible. Unfortunately, HF antennas are also too large at present to be used with small UAVs.